I don't know if the ROL BIG Archiver will work with the demo version, we have only tried the CD and DVD versions of the game. I may get around to testing it soon or you could try if you'd like.
The demo contains a few maps for single and multiplayer (human and pc ai) skirmish games and a few missions from the second chapter of the single player campaign, set in the Alin desert lands.
The CD or DVD version contains the full game of 3 chapters for the single player campaign, dozens of maps for skirmish games, and a scenario editor.
The ROL BIG Archiver allows the .BIG files to be extracted to use more game content such as building, unit, spell, etc skin graphics, 3D models, xml data, etc.
"Max settings" means maximum graphics settings, you can choose to show less or more graphics and other features in the options menus.
If your computer is good the game looks better when all the graphics are set on high/maximum.
Also check your email for another reply.
[This message has been edited by alincarpetman (edited 06-01-2016 @ 06:49 PM).]